In general, a hydraulic excavator as a typical example of a construction machine is composed of an automotive lower traveling structure, an upper revolving structure rotatably mounted on the lower traveling structure, and a working mechanism tiltably provided on a front side of the upper revolving structure.
Here, the hydraulic excavator includes a small-sized hydraulic excavator for performing a work in a narrow work site or the like where obstructions are present on the periphery. This small-sized hydraulic excavator is called a small revolving-type excavator or a rear small revolving-type excavator, for example. These small-sized hydraulic excavators are configured such that a counterweight is formed having an arc shape and is arranged at a position close to a revolving center so that, when the upper revolving structure operates to revolve, its rear side is substantially accommodated in a vehicle width of the lower traveling structure.
The upper revolving structure of the small-sized hydraulic excavator is composed of a revolving frame forming a support structural body, an engine mounted on a rear side of the revolving frame and driving a hydraulic pump, a cooling fan generating a cooling air in a sucking direction by being rotated/driven by the engine, a radiator provided by being faced with the cooling fan and cooling the engine coolant by passage of the cooling air generated by the cooling fan, and an oil cooler for cooling the hydraulic oil by the cooling air. The radiator and the oil cooler are arranged in parallel with respect to a flow direction of the cooling air so that the both can receive the cold cooling air (see, Patent Document 1, for example).